Baking a Better Rocket

Mechanical and materials engineering students Jack Slocum and Sam Arnold rarely shy away from a challenge. As PSU students they’ve designed electronics packaging for remote sensors in the SWEETLAB, helped develop automated water samplers used by the U.S. Geological Service and the Environmental Protection Agency to monitor degraded waterways and built a Formula SAE race car that cruised to a best-ever 16th place finish out of a field of 77 at a national competition.

Now in their senior year, Slocum, Arnold and their fellow senior capstone team members Barrett Strecker, Rob Melchione, and Tung Nguyen, one of PSU’s Intel Vietnam Scholars, are taking on their most challenging project yet – designing and building a carbon fiber airframe for Portland State Aerospace Society’s (PSAS) next launch vehicle.

“Early in the fall, our paths crossed with Andrew Greenberg as he was setting up the PSAS rocket for an open house,” recalls Slocum. “We were looking for a capstone project and he was looking for someone to take airframe design to the next level. Having had some experience with composites from Viking Motorsports, we jumped at the opportunity.”

Fabrication of the carbon fiber cylinders required an automated curing oven for carbon composites; a prohibitively expensive piece of machinery. Though it was possible to source access to an oven through a sponsor, as they had done with the race car, such access would be limited. For this project, freedom to experiment with the material was paramount. So, drawing from the knowledge gleaned from their 100-level sequence and numerous subsequent projects, the team engineered a custom curing oven.

“The temperature controls mimic the electrical controls of the projects we designed in our freshman year mechanical engineering class,” explains Arnold. “It’s a credit to the College that students are given the opportunity to dive into the engineering process right away through hands-on learning. It builds our confidence as engineers early so that we can take full advantage of our time as students.”

Once the oven was complete, the team moved on to the intensely iterative process of fine-tuning the mechanical design of the carbon fiber cylinders. Fabrication of the 3D-printed nylon carbon fiber parts was made possible by support from NW Rapid Manufacturing. This allowed the team to swiftly prototype and produce geometries that are almost impossible to make using traditional methods. Each member of the team put in an average of 30, at times very tedious, hours every week, recording every experiment and accounting for every variable.

“We did minimal documentation for Viking Motorsports – and it was continually a serious problem. This time we have more than 350 pages of documentation, along with detailed records of all manufactured parts and baking cycles,” said Slocum. “We’ve been quite meticulous and it has paid off. So far multiple people have been able to reproduce five high-quality modules without any prior experience.”

Previously composed of aluminum, the new rocket body is made from composite materials donated by ACES, an industrial supplier for Boeing. The material is state-of the art, but has surpassed its expiration date. Deemed less than safe for a vehicle that carries passengers, it is perfectly suitable for an unmanned rocket.

On track to complete their project in time for an August 2014 launch, it is anticipated that the new airframe will be 75% lighter than the previous rocket body - a substantial upgrade to a system that’s sole mission is the pursuit of earth’s orbit.

As the team prepares for life after graduation, not only do they leave with an impressive portfolio. They will also leave behind a significant upgrade to Maseeh College's fabrication capabilities - a new composite lab and a roadmap for future students in pursuit of the limits of their own ingenuity.Learn more about the Portland State Aerospace Society and its open source rocket science projects at http://psas.pdx.edu/.